The millimeter wave frequency band is becoming an increasingly attractive option in a broad range of products and services, including high-speed, point-to-point wireless local area networks, broadband Internet access, and point-to-multipoint communications. Other examples include satellite, radar, mobile collision detection, and imaging. Because of shorter wavelengths, the millimeter wave frequency band permits the use of smaller antennas than would typically be called for under similar circumstances in the lower bands to achieve the same high directivity and high gain. A consequence of this high directivity is the possibility of a more efficient use of the spectrum. That is, a greater number of highly directive antennas can be placed in a given area than less directive antennas. The net result is higher reuse of the spectrum and a higher density of users as compared to lower frequencies.
Unfortunately, the development of millimeter wave (MMW) devices has been hindered in part by difficulties associated with the design and development of the radiating structures, i.e., antennas, for MMW devices, and more particularly, with forming interconnects between an integrated circuit and the radiating structures. One approach for integrating an antenna in a MMW device involves printing a planar antenna, such as a microstrip or patch antenna, on a circuit board, or substrate, and forming interconnects between an integrated circuit die and the antenna. Such planar antennas may be relatively low cost and can be readily manufactured and integrated within a MMW device. However, discontinuities of chip interconnects, like bond wires, between a transceiver and the planar antenna are difficult to control due to the extremely short wavelength of a millimeter band wave, i.e., on the order of one to ten millimeters. Consequently, chip interconnect discontinuities are a critical limiting factor in antenna performance. Furthermore, this microstrip or patch antenna printed on the circuit board has the undesirable effect of utilizing valuable real estate on the circuit board. Wire antennas or cavity antennas have also been considered for use with MMW devices as alternatives to printed-circuit patch antennas due to their broad bandwidth, low loss, and reduced dependence on substrate real estate. However, fabrication difficulty has limited their implementation in a cost effective and integrated manner.
Accordingly, what is needed is an antenna structure that does not suffer from interconnect discontinuities, is small, and is cost effectively fabricated using existing manufacturing processes.